/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */

#include <iostream>

using namespace std;

struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
};

class Solution {
public:
    TreeNode* invertTree(TreeNode* root) {
        if(root == nullptr) {
            return root;
        }

        TreeNode *tmp = nullptr;
        tmp = root->left;
        root->left = root->right;
        root->right = tmp;

        invertTree(root->left);
        invertTree(root->right);

        return root;
    }
};

int main()
{
    return 0;
}